!<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var n1 = prompt('请输入第一个数：');
        var n2 = prompt('请输入第二个数：');
        console.log(Number(n1) + Number(n2));// 33
        console.log(n1 - 0 + (n2 - 0));// 33
        console.log(parseInt(n1) + parseInt(n2));// 33
    </script>
</body>
</html>